1. Field of the Invention
The present invention relates to an image forming apparatus, and, more particularly, to an image forming apparatus having a configuration suitable for size reduction.
2. Description of the Related Art
An image forming apparatus is an apparatus to form an image on a printing medium. Examples of the image forming apparatus include, e.g., printers, copiers, facsimiles, and devices with some combination of functions of these.
A color image forming apparatus adopting an electronic photography may be a type that are often referred to as a “tandem image forming apparatus.” A tandem image forming apparatus has photosensitive members provided in equal number to the number of colors of toners used in printing. Most commonly, a color image forming apparatus uses four toner colors, specifically, yellow, magenta, cyan, and black. Therefore, the tandem image forming apparatus includes four photosensitive members corresponding to the respective colors.
FIG. 1 is a view schematically illustrating a configuration of a conventional tandem image forming apparatus. As shown in FIG. 1, the conventional tandem image forming apparatus 1 includes a plurality of photosensitive members 2K, 2C, 2M, and 2Y, a light scanning device 3 to form electrostatic latent images on the photosensitive members by scanning the respective photosensitive members, and a plurality of developers 4K, 4C, 4M, and 4Y.
The photosensitive members 2K, 2C, 2M, and 2Y are arranged in vertical alignment with respect to each other, each being rotatable, and contacting the intermediate transfer belt 5.
The light scanning device 3 includes a first scanning optical system 3a having a first light deflector 3c, and a second scanning optical system 3b having a second light deflector 3d. Light beams, emitted from a first light source (not shown) and a second light source (not shown) of the first scanning optical system 3a, are deflected, from the first light deflector 3c, into different directions. Then, the deflected light beams are introduced to the first photosensitive member 2K and second photosensitive member 2C via reflecting mirrors 3e and 3f, producing an electrostatic latent image on each of the photosensitive members. Also, light beams, emitted  from a third light source (not shown) and a fourth light source (not shown) of the second  scanning optical system 3b, are deflected, from the second light deflector 3d, into different  directions. Then, the deflected light beams are introduced to the third photosensitive member  2M and fourth photosensitive member 2Y via reflecting mirrors 3g and 3h, producing an  electrostatic latent image on each of the photosensitive members.
The developers 4K, 4C, 4M, and 4Y supply a developing agent to the electrostatic latent images formed on the respective photosensitive members 2K, 2C, 2M, and 2Y, to develop the electrostatic latent images into visible images. The resulting visible images on the respective photosensitive members 2K, 2C, 2M, and 2Y are sequentially transferred to the intermediate transfer belt 5 in such a manner that they overlap one another. As a result, a completed color image is formed on intermediate transfer belt 5. The color image is finally transferred to a printing medium S passing through a gap between the intermediate transfer belt 5 and a transfer roller 6.
The above-described tandem image forming apparatus is advantageous for high-speed printing. However, due to the fact that photosensitive members must be provided in equal number to the number of colors of toner and the fact that there is a need for optical systems to scan the respective photosensitive members, tandem image forming apparatuses tend to be large in size.
In particular, in the configuration as shown in FIG. 1, in which the photosensitive members 2K, 2C, 2M, and 2Y are in the vertical in-line arrangement, it is difficult to reduce the overall height of the image forming apparatus, and exacerbates the difficulties in reducing the size of the image forming apparatus.
Furthermore, when using the intermediate transfer belt 5 as shown in FIG. 1, vibration caused during circulation of the belt 5 may make it difficult to achieve accurate color registration, and consequently, to achieve a high-quality print image.